A. Field of Endeavor
The present disclosure relates to sunscreen compositions that have improved water resistance.
B. Background Information
Sun protection products have evolved considerably from the white titanium oxide stripe on a life guard's nose to advanced organic sunscreen compositions that provide broad spectrum protection from ultraviolet (UV) radiation in the UVA region (320 to 400 nm) and UVB region (290 to 320 nm). Protection from UVA radiation is measured as a Protection Factor—UVA or PFA. Protection from UVB radiation is measured as a Sun Protection Factor or SPF.
Active consumers today not only seek broad spectrum sun protection, but they also want water resistance while enjoying water activities. Sunscreen manufacturers provide the consumer with a water resistance rating that is dictated by the 2011 U.S. Food & Drug Administration (FDA) final monograph for water resistance wherein a sunscreen composition must meet the critical wavelength of 370 nm after water immersion for 40 minutes for a rating of water resistant (WR) or 80 minutes for a rating of very water resistant (VWR). However, the critical wavelength protocol does not take into account the efficacy of the sunscreen composition after exposure to real life conditions of heat, sweat, salt water or chlorinated pool water. Under these conditions of heat, salt, and/or chemicals, the sunscreen composition can lose its efficacy and provide limited or no protection to the consumer. Furthermore, when the sunscreen composition is exposed to excessive heat, for example, when it is stored in a hot car, the sunscreen product will thin out and become difficult to apply. The heat may also affect the efficacy of the sunscreen actives as well.
United States Patent Application No. 2011/0269839 is directed to a water soluble thermo gelling polymer for treating and/or preventing snoring that is a liquid in the packaging, but upon contact with mucus membranes at 37° C., becomes a gel. While the thermo gelling makes it possible to target a treatment area within the body, it is unclear whether the thereto gelling polymer will withstand adverse conditions of continuous contact with water, in particular, salt or pool water.
United States Patent Application No. 2014/0170192 discloses a sunscreen composition that includes at least one UV filter, at least one booster, at least one thermo sensitive polymer, and at least one wetting agent. The sunscreen compositions exhibit a high SPF mainly due to the use of very specific ratios of sunscreen actives in combination with a SPF booster such as, SUNSPHERES® glass microspheres. However, since both the thermo sensitive polymer and wetting agent are both highly water soluble, they will contribute little in the way of water resistance.
U.S. Pat. No. 7,339,013 is directed to a thermo sensitive polymer and its synthesis. Aqueous solutions of the polymers can be applied at low viscosity to the body. The polymers then gellify with an increase in temperature such as when applied to human skin. However, there is no suggestion given its water solubility that when incorporated into a sunscreen composition, the polymers would provide enhanced water resistance under adverse conditions that include sweat and/or chlorine.
Thus, there is a need to provide a more robust sunscreen formulation that preserves the efficacy and water resistance of the sunscreen composition after exposure to heat, sweat, salt water, and other adverse conditions.